Interface-induced concentration enhancement in glycine solutions investigated using surface plasmon resonance spectroscopy and molecular dynamics simulations

Ruairidh Mackay; Mozhdeh Mohammadpour; Binoy Paulose Nadappuram; Karen Johnston; Jan Sefcik; King Hang Aaron Lau

doi:10.1021/acs.jpclett.5c03688

Interface-induced concentration enhancement in glycine solutions investigated using surface plasmon resonance spectroscopy and molecular dynamics simulations

Ruairidh Mackay, Mozhdeh Mohammadpour, Binoy Paulose Nadappuram, Karen Johnston, Jan Sefcik^*, King Hang Aaron Lau^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

Abstract

Recent molecular simulations indicate nanoscale heterogeneity at liquid–solution interfaces, which is expected to significantly impact interfacial processes, such as catalysis and nucleation. We investigate the enhancement of glycine concentration in aqueous solutions at solid interfaces using molecular dynamics (MD) simulations and surface plasmon spectroscopy (SPR) measurements. MD predicts an interfacial concentration enhancement in a nanoscale solution region at the solid surface. SPR shows for the first time direct experimental evidence of such an enhancement in small molecule liquid mixtures. The excess interfacial mass density on gold and polystyrene surfaces for undersaturated glycine solutions reaches up to ∼50 ng/cm2, corresponding to a 1 nm layer with over double the glycine saturation concentration. We attribute the interfacial enhancement to omnipresent van der Waals interactions between solution components and surfaces. We expect this effect to be a common phenomenon in solutions that is likely to have profound effects on both natural and industrial interfacial processes.

Original language	English
Pages (from-to)	5535–5540
Number of pages	6
Journal	The Journal of Physical Chemistry Letters
Volume	17
Issue number	19
Early online date	4 May 2026
DOIs	https://doi.org/10.1021/acs.jpclett.5c03688
Publication status	Published - 14 May 2026

Funding

We would like to acknowledge support for R.M. and J.S. from the EPSRC Future Continuous Manufacturing and Advanced Crystallisation Research Hub (Grant Ref: EP/P006965/1) for funding this work. We would also like to thank Dr. B Paulose (Department of Pure & Applied Chemistry, University of Strathclyde) for his help in preparing the sample gold substrates utilised in this study. M.M. was supported by a Leverhulme Trust Research Project Grant (RPG-2019-197). K.H.A.L. also acknowledges The Royal Society Research Grant RG150687 for supporting development of the custom-built SPR setup, and we acknowledge support of David McKechnie and Samira Anker for their assistance with the MD simulations and analysis.

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

SDG 3 Good Health and Well-being

Keywords

SPR
surface resonance spectroscopy
glycine
crystallization

Access to Document

10.1021/acs.jpclett.5c03688Licence: CC BY 4.0

Mackay-etal-JPCL-2026-Interface-induced-concentration-enhancement-in-glycine-solutions-investigatedFinal published version, 2.04 MBLicence: CC BY 4.0

https://doi.org/10.26434/chemrxiv-2025-0w18mLicence: CC BY-NC-SA 4.0

Catching nucleation in action using surface enhanced Raman spectroscopy
Johnston, K. (Principal Investigator), Faulds, K. (Co-investigator) & Sefcik, J. (Co-investigator)
Leverhulme Trust
1/09/20 → 30/12/23
Project: Research
Future Continuous Manufacturing and Advanced Crystallisation Research Hub (CMAC Hub)
Florence, A. (Principal Investigator), Brown, C. (Co-investigator), Halbert, G. (Co-investigator), Johnston, B. (Co-investigator), Markl, D. (Co-investigator), Nordon, A. (Co-investigator), Price, C. J. (Co-investigator), Sefcik, J. (Co-investigator) & Ter Horst, J. (Co-investigator)
EPSRC (Engineering and Physical Sciences Research Council)
1/01/17 → 30/09/24
Project: Research

Data for "Interface-Induced Concentration Enhancement in Glycine Solutions Investigated Using Surface Plasmon Resonance Spectroscopy and Molecular Dynamics Simulations"
Mohammadpour, M. (Creator) & Johnston, K. (Creator), University of Strathclyde, 9 Apr 2026
DOI: 10.15129/e31ae64a-1a03-4c84-b9ba-274ab2cc7929
Dataset

ARCHIE-WeSt (UOSHPC)
Martin, R. (Manager)
University Of Strathclyde
Facility/equipment: Facility

Cite this

Mackay, R., Mohammadpour, M., Paulose Nadappuram, B., Johnston, K., Sefcik, J., & Lau, K. H. A. (2026). Interface-induced concentration enhancement in glycine solutions investigated using surface plasmon resonance spectroscopy and molecular dynamics simulations. The Journal of Physical Chemistry Letters, 17(19), 5535–5540. https://doi.org/10.1021/acs.jpclett.5c03688

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title = "Interface-induced concentration enhancement in glycine solutions investigated using surface plasmon resonance spectroscopy and molecular dynamics simulations",

abstract = "Recent molecular simulations indicate nanoscale heterogeneity at liquid–solution interfaces, which is expected to significantly impact interfacial processes, such as catalysis and nucleation. We investigate the enhancement of glycine concentration in aqueous solutions at solid interfaces using molecular dynamics (MD) simulations and surface plasmon spectroscopy (SPR) measurements. MD predicts an interfacial concentration enhancement in a nanoscale solution region at the solid surface. SPR shows for the first time direct experimental evidence of such an enhancement in small molecule liquid mixtures. The excess interfacial mass density on gold and polystyrene surfaces for undersaturated glycine solutions reaches up to ∼50 ng/cm2, corresponding to a 1 nm layer with over double the glycine saturation concentration. We attribute the interfacial enhancement to omnipresent van der Waals interactions between solution components and surfaces. We expect this effect to be a common phenomenon in solutions that is likely to have profound effects on both natural and industrial interfacial processes.",

keywords = "SPR, surface resonance spectroscopy, glycine, crystallization",

author = "Ruairidh Mackay and Mozhdeh Mohammadpour and \{Paulose Nadappuram\}, Binoy and Karen Johnston and Jan Sefcik and Lau, \{King Hang Aaron\}",

year = "2026",

month = may,

day = "14",

doi = "10.1021/acs.jpclett.5c03688",

language = "English",

volume = "17",

pages = "5535–5540",

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Mackay, R, Mohammadpour, M, Paulose Nadappuram, B , Johnston, K , Sefcik, J & Lau, KHA 2026, 'Interface-induced concentration enhancement in glycine solutions investigated using surface plasmon resonance spectroscopy and molecular dynamics simulations', The Journal of Physical Chemistry Letters, vol. 17, no. 19, pp. 5535–5540. https://doi.org/10.1021/acs.jpclett.5c03688

Interface-induced concentration enhancement in glycine solutions investigated using surface plasmon resonance spectroscopy and molecular dynamics simulations. / Mackay, Ruairidh; Mohammadpour, Mozhdeh; Paulose Nadappuram, Binoy et al.
In: The Journal of Physical Chemistry Letters, Vol. 17, No. 19, 14.05.2026, p. 5535–5540.

Research output: Contribution to journal › Article › peer-review

TY - JOUR

T1 - Interface-induced concentration enhancement in glycine solutions investigated using surface plasmon resonance spectroscopy and molecular dynamics simulations

AU - Mackay, Ruairidh

AU - Mohammadpour, Mozhdeh

AU - Paulose Nadappuram, Binoy

AU - Johnston, Karen

AU - Sefcik, Jan

AU - Lau, King Hang Aaron

PY - 2026/5/14

Y1 - 2026/5/14

N2 - Recent molecular simulations indicate nanoscale heterogeneity at liquid–solution interfaces, which is expected to significantly impact interfacial processes, such as catalysis and nucleation. We investigate the enhancement of glycine concentration in aqueous solutions at solid interfaces using molecular dynamics (MD) simulations and surface plasmon spectroscopy (SPR) measurements. MD predicts an interfacial concentration enhancement in a nanoscale solution region at the solid surface. SPR shows for the first time direct experimental evidence of such an enhancement in small molecule liquid mixtures. The excess interfacial mass density on gold and polystyrene surfaces for undersaturated glycine solutions reaches up to ∼50 ng/cm2, corresponding to a 1 nm layer with over double the glycine saturation concentration. We attribute the interfacial enhancement to omnipresent van der Waals interactions between solution components and surfaces. We expect this effect to be a common phenomenon in solutions that is likely to have profound effects on both natural and industrial interfacial processes.

AB - Recent molecular simulations indicate nanoscale heterogeneity at liquid–solution interfaces, which is expected to significantly impact interfacial processes, such as catalysis and nucleation. We investigate the enhancement of glycine concentration in aqueous solutions at solid interfaces using molecular dynamics (MD) simulations and surface plasmon spectroscopy (SPR) measurements. MD predicts an interfacial concentration enhancement in a nanoscale solution region at the solid surface. SPR shows for the first time direct experimental evidence of such an enhancement in small molecule liquid mixtures. The excess interfacial mass density on gold and polystyrene surfaces for undersaturated glycine solutions reaches up to ∼50 ng/cm2, corresponding to a 1 nm layer with over double the glycine saturation concentration. We attribute the interfacial enhancement to omnipresent van der Waals interactions between solution components and surfaces. We expect this effect to be a common phenomenon in solutions that is likely to have profound effects on both natural and industrial interfacial processes.

KW - SPR

KW - surface resonance spectroscopy

KW - glycine

KW - crystallization

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DO - 10.1021/acs.jpclett.5c03688

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JO - The Journal of Physical Chemistry Letters

JF - The Journal of Physical Chemistry Letters

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Interface-induced concentration enhancement in glycine solutions investigated using surface plasmon resonance spectroscopy and molecular dynamics simulations

Abstract

Funding

UN SDGs

Keywords

Access to Document

Fingerprint

Projects

Catching nucleation in action using surface enhanced Raman spectroscopy

Future Continuous Manufacturing and Advanced Crystallisation Research Hub (CMAC Hub)

Datasets

Data for "Interface-Induced Concentration Enhancement in Glycine Solutions Investigated Using Surface Plasmon Resonance Spectroscopy and Molecular Dynamics Simulations"

Equipment

ARCHIE-WeSt (UOSHPC)

Cite this